JP3833834B2

JP3833834B2 - Valve operating device for internal combustion engine

Info

Publication number: JP3833834B2
Application number: JP29771198A
Authority: JP
Inventors: 信中村; 勉日比; 吉彦山田; 常靖野原
Original assignee: Hitachi Ltd; Nissan Motor Co Ltd
Current assignee: Hitachi Ltd; Nissan Motor Co Ltd
Priority date: 1998-10-20
Filing date: 1998-10-20
Publication date: 2006-10-18
Anticipated expiration: 2018-10-20
Also published as: JP2000120417A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば吸気弁あるいは排気弁の開閉時期及びバルブリフト量を機関運転状態に応じて可変にできる内燃機関の動弁装置に関する。
【０００２】
【従来の技術】
この種の従来の内燃機関の動弁装置としては、ＳＡＥ９７０３３８に記載されたものが知られている。
【０００３】
図１１に基づいて概略を説明すれば、機関のシリンダヘッド上に前後方向に沿って配置されて、機関のクランク軸によって回転駆動される駆動軸１と、該駆動軸１に揺動自在に支持されて、例えば吸気弁２のバルブリフター３の上面３ａに摺接して該吸気弁２を図外のバルブスプリングのばね力に抗して開作動させる揺動カム４と、駆動軸１と揺動カム４との間に設けられて、駆動軸１の回転力をリフト力に変換して揺動カム４に伝達する伝達機構５とを備えている。この伝達機構５は、駆動軸１の外周に固定された第１平歯車６と、該第１平歯車６の上方位置に配置されたクランクシャフト７と、該クランクシャフト７に固定されて第１平歯車６に噛合する第２平歯車８と、クランクシャフト７と揺動カム４とを連結ピン９を介して連係する連結リンク１０とから構成されている。
【０００４】
そして、駆動軸１及び第１平歯車６の一方向（矢印）の回転に伴い第２平歯車８及びクランクシャフト７が回転して連結リンク１０により揺動カム４を矢印方向へ揺動させる。これによって、揺動カム４は、下面のカム面４ａがバルブリフター３の上面３ａに摺接しながら吸気弁２をバルブスプリングのばね力に抗して押圧あるいは押圧を解除して開閉作動させるようになっている。したがって、バルブリフト特性は、比較的大きなリフト特性が得られる。
【０００５】
【発明が解決しようとする課題】
ところで、前記従来の可変動弁装置にあっては、駆動軸１の１回転中の揺動カム４のカム面４ａに対するバルブスプリングのばね反力の方向（法線ｈ）が、揺動カム４の枢支点である連結ピン９の内側、つまり図１２に示すように連結ピン９と駆動軸１との軸心間に常に位置するようになっている。
【０００６】
すなわち、揺動カム４がバルブリフター３の上面３ａを摺接しながら該バルブリフター３を押圧あるいは押圧を解除して吸気弁２を開閉作動している際に、バルブリフター３を介して揺動カム４に作用するバルブスプリングのばね反力方向（法線ｈ）が最小，最大リフト領域に拘わらず、常時連結ピン９と駆動軸１との軸心間に位置している。
【０００７】
このため、揺動カム４は、バルブスプリングのばね力によって連結ピン９と反対側、つまり駆動軸１側が常に上方に押圧された状態になり、したがって、駆動軸１に軸受された支持孔４ｄの内周面の下端部４ｅが駆動軸１の外周面１ａの下端部１ｂに常に圧接摺動した形になる。この結果、該両下端部１ｂ，４ｅの間に局部的な摩耗が発生し易くなり、耐久性が低下するおそれがある。
【０００８】
【課題を解決するための手段】
本発明は、前記従来の装置の実情に鑑みて案出されたもので、請求項１記載の発明は、機関のクランク軸に同期して回転し、外周に駆動カムが設けられた駆動軸と、シリンダヘッド内に摺動自在に支持されて、機関弁に押圧力を伝達するバルブリフターと、前記駆動軸あるいは該駆動軸と平行な支軸の外周面に支持孔を介して揺動自在に支持されていると共に、端部に設けられた枢支点に前記駆動カムの回転力を揺動力として伝達する伝達機構から揺動力が伝達されることにより、前記駆動カムの回転に伴い前記バルブリフターの上面を押圧してバルブスプリングのばね反力に抗して機関弁を開作動させる揺動カムと、を備えた内燃機関の動弁装置であって、前記バルブスプリングのばね反力による前記枢支点回りのモーメントにより前記支持孔の内周面と前記駆動軸あるいは前記支軸の外周面との間に作用する荷重方向が反転するような位置に前記枢支点を配置したことを特徴としている。
【０００９】
本発明によれば、機関弁の例えば大バルブリフト領域において、揺動カムがバルブリフターの上面上を摺接している際に、バルブスプリングのばね反力の方向はベースサークル領域では揺動カムの枢支点から駆動軸との間に位置するものの、リフト領域では枢支点を中心として駆動軸と反対側に移動することになる。したがって、枢支点から駆動軸との間に位置する間では、揺動カムの支持孔の駆動軸に対する圧接摺動位置が支持孔の内周面下端部になるが、駆動軸と反対側に位置する間では、揺動カムは枢支点を中心に駆動軸側が下方へ反転する方向に力が作用するため、駆動軸に対する圧接摺動位置が支持孔の内周面の上端部側になる。このため、揺動カムの支持孔の内周面と駆動軸の外周面との間に局部的な摩耗の発生が防止される。
【００１０】
請求項２記載の発明は、機関のクランク軸に同期して回転し、外周に駆動カムが設けられた駆動軸と、シリンダヘッド内に摺動自在に支持されて、機関弁に押圧力を伝達するバルブリフターと、前記駆動軸あるいは該駆動軸と平行な支軸の外周面に支持孔を介して揺動自在に支持されていると共に、端部に設けられた枢支点に前記駆動カムの回転力を揺動力として伝達する伝達機構から揺動力が伝達されることにより、前記駆動カムの回転に伴い前記バルブリフターの上面を押圧してバルブスプリングのばね反力に抗して機関弁を開作動させる揺動カムと、機関運転状態に応じて前記機関弁のバルブリフト量が小さく制御されている状態では、前記バルブスプリングのばね反力による前記支持孔の内周面と前記駆動軸あるいは前記支軸の外周面との間の荷重方向が常に一方側となり、前記可変機構によりバルブリフト量が大きく制御されている状態では、前記バルブスプリングのばね反力による前記枢支点回りのモーメントにより、前記支持孔の内周面と前記駆動軸あるいは支軸の外周面との間に作用する荷重方向が反転するような位置に前記枢支点を配置したことを特徴としている。
【００１１】
したがって、機関運転状態に応じてバルブタイミングおよびバルブリフト量を可変にできることにより、機関性能を十分に発揮させることができる。
【００１２】
請求項３記載の発明にあっては、前記伝達機構は、一端部が駆動カムの外周に摺動自在に嵌合したリンクアームと、支持軸に揺動自在に設けられて、一端部がリンクアームの他端部に回転自在に連係したロッカアームと、一端部がロッカアームの他端部に連係し、他端部が揺動カムの端部に回転自在に連結して前記枢支点を構成するリンクロッドとを備えたことを特徴としている。
【００１３】
したがって、前記揺動カムは、伝達機構によって常にその揺動範囲が制御されるため、例えば機関高回転時における所定以上の過度な揺動を規制することが可能になる。
【００１４】
請求項４記載の発明は、前記駆動軸の内部軸方向に油通路を形成すると共に、該駆動軸の周壁に前記油通路と揺動カムの支持孔内周面とを連通する油孔を形成したことを特徴としている。
【００１５】
したがって、揺動カムの支持孔内周面と駆動軸の外周面との間の潤滑性が向上して、両者間の摩耗の発生をさらに防止することができる。
【００１６】
請求項５記載の発明は、前記バルブリフターの揺動カムと摺接する上面を円弧状に形成したことを特徴としている。
【００１７】
この発明によれば、バルブリフターに対する揺動カムのカム面の当接位置を変化させることができ、したがってバルブスプリングのばね反力の方向を枢支点から駆動軸の反対側に容易に設定することができる。
【００１８】
【発明の実施の形態】
以下、本発明の動弁装置の実施形態を図面に基づいて詳述する。この実施形態の動弁装置は、１気筒あたり２つの吸気弁を備えかつ吸気弁のバルリフト量を機関運転状態に応じて可変にする可変機構を備えたものを示している。
【００１９】
すなわち、この動弁装置は、シリンダヘッド１１に図外のバルブガイドを介して摺動自在に設けられた一対の吸気弁１２，１２と、シリンダヘッド１１上部の軸受１４に回転自在に支持された中空状の駆動軸１３と、該駆動軸１３に圧入等により固設された偏心回転カムである２つの駆動カム１５，１５と、駆動軸１３の外周面１３ａに揺動自在に支持されて、各吸気弁１２，１２の上端部に配設されたバルブリフター１６，１６に摺接して各吸気弁１２，１２を開作動させる揺動カム１７，１７と、駆動カム１５と揺動カム１７，１７との間に連係されて、駆動カム１５の回転力を揺動カム１７，１７の揺動力として伝達する伝達機構１８と、該伝達機構１８の作動位置を可変にする可変機構１９とを備えている。
【００２０】
前記駆動軸１３は、機関前後方向に沿って配置されていると共に、一端部に設けられた図外の従動スプロケットや該従動スプロケットに巻装されたタイミングチェーン等を介して機関のクランク軸から回転力が伝達されており、この回転方向は図１中反時計方向に設定されている。また、この駆動軸１３の内部軸方向には、図外のオイルメインギャラリに連通する油通路１３ｂが形成されていると共に、周壁に一端が油通路１３ｂに開口し、他端が外周面１３ａと揺動カム１７，１７の後述する支持孔２０ａ内周面との間に開口した油孔１３ｃが径方向に沿って貫通形成されている。
【００２１】
前記軸受１４は、シリンダヘッド１１の上端部に設けられて駆動軸１３の上部を支持するメインブラケット１４ａと、該メインブラケット１４ａの上端部に設けられて後述する支持軸である制御軸３２を回転自在に支持するサブブラケット１４ｂとを有し、両ブラケット１４ａ，１４ｂが一対のボルト１４ｃ，１４ｃによって上方から共締め固定されている。
【００２２】
前記両駆動カム１５は、図４にも示すように、ほぼリング状を呈し、小径なカム本体１５ａと、該カム本体１５ａの外端面に一体に設けられたフランジ部１５ｂとからなり、内部軸方向に駆動軸挿通孔１５ｃが貫通形成されていると共に、カム本体１５ａの軸心Ｘが駆動軸１３の軸心Ｙから径方向へ所定量だけオフセットしている。また、この各駆動カム１５は、駆動軸１３に対し前記両バルブリフター１６，１６に干渉しない両外側に駆動軸挿通孔１５ｃを介して圧入固定されていると共に、両方のカム本体１５ａ，１５ａの外周面１５ｄ，１５ｄが同一のカムプロフィールに形成されている。
【００２３】
前記バルブリフター１６，１６は、有蓋円筒状に形成され、シリンダヘッド１１の保持孔内に摺動自在に保持されていると共に、揺動カム１７，１７が摺接する上面１６ａ，１６ａが機関巾方向に沿って円弧状に形成されている。
【００２４】
前記揺動カム１７は、図１〜図３及び図６，図７に示すようにほぼ横Ｕ字形状を呈し、ほぼ円環状の基端部２０に駆動軸１３が嵌挿されて回転自在に支持される支持孔２０ａが貫通形成されていると共に、一端部のカムノーズ部２１にピン孔２１ａが貫通形成されている。また、揺動カム１７の下面には、カム面２２が形成され、基端部２０側の基円面２２ａと該基円面２２ａからカムノーズ部２１側に円弧状に延びるランプ面２２ｂと該ランプ面２２ｂからカムノーズ部２１の先端側に有する最大リフトの頂面２２ｃに連なるリフト面２２ｄとが形成されており、該基円面２２ａとランプ面２２ｂリフト面２２ｄ及び頂面２２ｃとが、揺動カム１７の揺動位置に応じて各バルブリフター１６の上面１６ａ所定位置に当接するようになっている。
【００２５】
すなわち、図５に示すバルブリフト特性からみると、図１に示すように基円面２２ａの所定角度範囲θ１がベースサークル区間になり、ランプ面２２ｂの前記ベースサークル区間θ１から所定角度範囲θ２がいわゆるランプ区間となり、さらにランプ面２２ｂのランプ区間θ２から頂面２２ｃまでの所定角度範囲θ３がリフト区間になるように設定されている。
【００２６】
前記伝達機構１８は、駆動軸１３の上方に配置されたロッカアーム２３と、該ロッカアーム２３の一端部２３ａと駆動カム１５とを連係するリンクアーム２４と、ロッカアーム２３の他端部２３ｂと揺動カム１７とを連係するリンクロッド２５とを備えている。
【００２７】
前記各ロッカアーム２３は、図３に示すように平面からみてほぼクランク状に折曲形成され、中央に有する筒状基部２３ｃが後述する制御カム３３に回転自在に支持されている。また、各筒状基部２３ｃの各外端部に突設された前記一端部２３ａには、ピン２６が嵌入するピン孔２３ｄが貫通形成されている一方、各基部２３ｃの各内端部に夫々突設された前記他端部２３ｂには、各リンクロッド２５の一端部２５ａと連結するピン２７が嵌入するピン孔２３ｅが形成されている。
【００２８】
また、前記リンクアーム２４は、比較的大径な円環状の基部２４ａと、該基部２４ａの外周面所定位置に突設された突出端２４ｂとを備え、基部２４ａの中央位置には、前記駆動カム１５のカム本体１５ａの外周面に回転自在に嵌合する嵌合孔２４ｃが形成されている一方、突出端２４ｂには、前記ピン２６が回転自在に挿通するピン孔２４ｄが貫通形成されている。
【００２９】
さらに、前記リンクロッド２５は、図１にも示すように所定長さの直線状に形成され、円形状の両端部２５ａ，２５ｂには前記ロッカアーム２３の他端部２３ｂと揺動カム１７のカムノーズ端部２１の各ピン孔２３ｅ，２１ａに圧入した各ピン２７，２８の端部が回転自在に挿通するピン挿通孔２５ｃ，２５ｄが貫通形成されており、前記ピン２８の軸心２８ａが揺動カム１７の枢支点になっている。
【００３０】
そして、バルブリフター１６，１６の上面１６ａ，１６ａを円弧状に形成することによって、前記駆動カム１５，１５の回転中における揺動カム１７，１７とバルブリフター１６，１６の移動当接点に作用するバルブスプリングのばね反力方向である法線ｈ位置が、図７Ａ，Ｂに示すように吸気弁１２の最大リフト領域でピン２８の軸心２８ａを中心として駆動軸１３側寄りと該駆動軸１３と反対側に変化させるようになっている。すなわち、揺動カム１７，１７のベースサークル領域では、図７Ａに示すようにバルブスプリングのばね反力Ｆ₁方向である法線ｈ₁は吸気弁１２のバルブステムの軸線方向に沿って図中垂直方向になり、軸心２８ａから駆動軸１３側寄りになっているが、リフト領域では、図７Ｂに示すようにばね反力Ｆ₂の方向である法線ｈ₂は揺動カム１７，１７がバルブリフター１６，１６の外周縁に当接するために軸心２８ａを挟んだ駆動軸１３と反対側の位置になるように設定されている。
【００３１】
一方、吸気弁１２，１２の小作動角域では、図６Ａ，Ｂに示すように揺動カム１７，１７はバルブリフター１６，１６の上面１６ａ，１６ａのほぼ中央位置に常時当接するため、法線ｈ₁，ｈ₂が軸心２８ａよりも駆動軸１３側に位置するように設定されている。
【００３２】
尚、各ピン２６，２７，２８の一端部には、リンクアーム２４やリンクロッド２５の軸方向の移動を規制するスナップリング２９，３０，３１，が設けられている。
【００３３】
前記可変機構１９は、駆動軸１３の上方位置に同じ軸受１４に回転自在に支持された制御軸３２と、該制御軸３２の外周に固定されてロッカアーム２３の揺動支点となる制御カム３３とを備えている。
【００３４】
前記各制御カム３３は、夫々円筒状を呈し、図１に示すように軸心Ｐ１位置が制御軸３２の軸心Ｐ２からα分だけ偏倚している。
【００３５】
前記制御軸３２は、駆動軸１３と並行に延設されて、一端部に設けられた図外の電磁アクチュエータによって所定回転角度範囲内で回転するように制御されており、前記電磁アクチュエータは、機関の運転状態を検出する図外のコントローラからの制御信号によって駆動するようになっている。コントローラは、クランク角センサやエアーフローメータ，水温センサ等の各種のセンサからの検出信号に基づいて現在の機関運転状態を演算等により検出して、前記電磁アクチュエータに制御信号を出力している。
【００３６】
以下、本実施形態の作用を説明すれば、まず、機関低速低負荷時には、コントローラからの制御信号によって電磁アクチュエータが一方に回転駆動される。このため、制御カム３３は、軸心Ｐ１が図６Ａ，Ｂに示すように制御軸３２の軸心Ｐ２から左上方の回動位置に保持され、厚肉部３３ａが駆動軸１３から上方向に離間移動する。このため、ロッカアーム２３は、全体が駆動軸１３に対して上方向へ移動し、このため、各揺動カム１７は、リンクロッド２５を介して端部２３が強制的に若干引き上げられて全体が左方向へ回動する。
【００３７】
したがって、図６Ａ，Ｂに示すように駆動カム１５が回転してリンクアーム２４を介してロッカアーム２３の一端部２３ａを押し上げると、そのリフト量がリンクロッド２５を介して揺動カム１７及びバルブリフター１６に伝達されるが、そのリフト量Ｌ１は図６Ｂに示すように比較的小さくなる。
【００３８】
よって、かかる低速低負荷域では、図８の破線で示すようにバルブリフト量が小さくなると共に、各吸気弁１２の開時期が遅くなり、排気弁とのバルブオーバラップが小さくなる。このため、燃費の向上と機関の安定した回転が得られる。
【００３９】
また、この小バルブリフト領域では、バルブスプリングのばね反力Ｆ₁，Ｆ₂の法線ｈ₁，ｈ₂は、軸心２８ａよりも駆動軸１３側寄りになっているため、揺動カム１７，１７の支持孔２０ａ，２０ａ内周面から駆動軸１３の外周面１３ａに作用する力ｆ₁，ｆ₂は内周面の下端部２０ｂと外周面１３ａの下端部１３ｄの一帯に掛かる。しかし、この時点での揺動カム１７，１７の揺動バルブリフト量は小さいため、バルブスプリングからのばね反力自身が小さく両下端部１３ｄ，２０ｂ間の摩耗の発生は少ない。しかも、この時点では、法線ｈ₁，ｈ₂が揺動カム１７の揺動中心側の領域内だけを移動するようになっているため、より小さなバルブリフトを実現できる。
【００４０】
一方、機関高速高負荷時に移行した場合は、コントローラからの制御信号によって電磁アクチュエータが反対方向に回転駆動される。したがって、図７Ａ，Ｂに示すように制御軸３２が、制御カム３３を図６に示す位置から反時計方向に回転させ、軸心Ｐ１（厚肉部３３ａ）を下方向へ移動させる。このため、ロッカアーム２３は、今度は全体が駆動軸１３方向（下方向）に移動して他端部２３ｂが揺動カム１７のカムノーズ部２１をリンクロッド２５を介して下方へ押圧して該揺動カム１７全体を所定量だけ時計方向へ回動させる。
【００４１】
したがって、揺動カム１７のバルブリフター１６上面１６ａに対するカム面２２の当接位置が図７Ａ，Ｂに示すように右方向位置に移動する。このため、図７Ａに示すように駆動カム１５が回転してロッカアーム２３の一端部２３ａをリンクアーム２４を介して押し上げると、バルブリフター１６に対するそのリフト量Ｌ２は図７Ｂに示すように大きくなる。
【００４２】
よって、かかる高速高負荷域では、カムリフト特性が低速低負荷域に比較して大きくなり、図８の実線で示すようにバルブリフト量も大きくなると共に、各吸気弁１２の開時期が早くなると共に、閉時期が遅くなる。この結果、吸気充填効率が向上し、十分な出力が確保できる。
【００４３】
また、前述のようにかかる大バルブリフト領域すなわちバルブスプリングからのばね反力の大きい領域では、バルブリフター１６上面１６ａに対するカム面２２の当接位置が図７Ｂに示すように、最大リフト付近で上面１６ａの孔縁付近になるため、バルブスプリングのばね反力Ｆ₂の法線ｈ₂は軸心２８ａより外側、つまり軸心２８ａを挾んで駆動軸１３の反対側になる。したがって、揺動カム１７，１７は、全体が軸心２８ａを支点とした図中反時計回りのモーメントＭが作用し、今度は荷重ｆ₂で下方向へ押し付けられて、支持孔２０ａの内周面の上端部２０ｃが駆動軸１３外周面１３ａの上端部に圧接摺動するように荷重方向が反転する。
【００４４】
この結果、支持孔２０ａ内周面の下端部２０ｂと駆動軸１３の外周面１３ａの下端部１３ｄとの圧接摺動が回避され、該両下端部１３ｄ，２０ｂの局部的な発熱や摩耗の発生が防止される。
【００４５】
しかも、支持孔２０ａの内周面と駆動軸１３の外周面１３ａとの間には、油通路１３ｂ及び油孔１３ｃから潤滑油が供給されるため、両面間の潤滑性能が向上する。また、前述のように、荷重の反転時には潤滑油のいわゆる絞り膜効果が起きて、潤滑油の負荷能力が向上すると共に、荷重の反転時に両面間の接触部に潤滑油が強制的に供給されるため、両面間の摩耗の発生を一層防止することが可能になる。
【００４６】
また、揺動カム１７，１７は、伝達機構１８、特にリンクロッド２５によってその揺動範囲が制御されているため、機関高回転時などにおいて揺動速度が速くなっても所定以上の過度な揺動を規制することができる。
【００４７】
図９は本発明の第２の実施形態を示し、リンクロッド２５を駆動軸１３側が凹状となる円弧状に折曲形成すると共に、バルブリフター１６，１６の上面１６ａ，１６ａを平坦状に形成した。したがって、リンクロッド２５を円弧状に折曲形成することによって、第１実施形態と同様に吸気弁１２の最大リフト領域においてリフト域にバルブスプリングのはね反力の法線ｈ₂が軸心２８ａよりも外側に位置するように構成したものである。他の構成は第１の実施形態と同様である。
【００４８】
したがって、この実施形態も駆動軸１３の外周面１３ａと揺動カム１７，１７の支持孔２０ａの内周面との局部的な摩耗の発生が防止される。
【００４９】
図１０は本発明の第３の実施形態を示し、揺動カム２２が駆動軸１３とは独立した支軸１００に支承されている。また、この支軸１００の内部軸方向に油通路１０１が形成されていると共に、周壁に一端が揺動カム１７の支持孔２００に開口した油孔１０２が形成されている。この実施形態では、駆動軸１３に揺動カム２２からの力ｆ₂が作用しなくなるため、駆動軸１３の局部的な摩耗を防止でき耐久性が向上する。一方、支軸１００は前述（実施形態）と同じ原理で、耐摩耗性が向上する。尚、他の構成は第１の実施形態と同様である。
【００５０】
なお、本発明は前記実施形態の構成に限定されるものではなく、例えば本装置を排気弁側に適用することも可能であり、また可変機構１９を有しない装置にも適用することができる。
【００５１】
【発明の効果】
以上の説明で明らかなように、本発明の動弁装置によれば、前記バルブスプリングのばね反力による前記枢支点回りのモーメントにより前記支持孔の内周面と前記駆動軸あるいは前記支軸の外周面との間に作用する荷重方向が反転するような位置に前記枢支点を配置したため、揺動カムの支持孔内周面と駆動軸あるいは支軸の外周面との局部的な摩耗の発生を防止することができる。
【００５２】
請求項２記載の発明によれば、可変機構によって機関弁のバルブタイミングとバルブリフト量を可変にできるため、機関運転状態に応じた機関性能を充分に発揮させることができる。
【００５３】
請求項３記載の発明によれば、機械的な伝達機構によって、例えば機関高回転時における揺動カムの過度な揺動が規制され、したがってバルブタイミング及びバルブリフトを高精度に制御できる。
【００５４】
請求項４記載の発明によれば、揺動カムの支持孔内周面と駆動軸外周面との間の潤滑性能が大巾に向上し、両面間の摩耗の発生をさらに防止することが可能になる。
【００５５】
請求項５記載の発明によれば、バルブリフターに対する揺動カムのカム面の当接位置を変化させることができるため、バルブスプリングのばね反力の方向を枢支点から駆動軸と反対側の外側に容易に設定することができる。また、かかるバルブリフターの上面を円弧状に形成することにより、前述の揺動カムに対するバルブスプリングばね反力の反転モーメントを大きくすることが可能になるため、支持孔内周面と駆動軸外周面との摩耗低減効果を一層向上させることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施態様を示す図２のＡ−Ａ線断面図。
【図２】本実施態様を一部断面して示す側面図。
【図３】同実施態様の平面図。
【図４】同実施形態に供される駆動カムを示す斜視図。
【図５】揺動カムの基端面とカム面に対応したバルブリフト特性図。
【図６】Ａ，Ｂは低速低負荷時の作用を示す図２のＢ−Ｂ線断面図。
【図７】Ａ，Ｂは高速高負荷時の作用を示す図２のＢ−Ｂ線断面図。
【図８】本実施態様のバルブタイミングとバルブリフトの特性図。
【図９】本発明の第２の実施形態を示す断面図。
【図１０】本発明の第３の実施形態を示す断面図。
【図１１】従来の動弁装置を示す概略図。
【図１２】同従来の動弁装置の作用説明図。
【符号の説明】
１１…シリンダヘッド
１２…吸気弁
１３…駆動軸
１３ａ…外周面
１３ｄ…下端部
１３ｅ…上端部
１５…駆動カム
１６…バルブリフター（フォロワ）
１７…揺動カム
１８…伝達機構
１９…可変機構
２０…基部
２０ａ…支持孔
２０ｂ…下端部
２０ｃ…上端部
２１…一端部
２２…カム面
２３…ロッカアーム
２３ａ，２３ｂ…端部
２４…リンクアーム
２５…リンクロッド
２８…ピン
２８ａ…軸心（枢支点）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve operating apparatus for an internal combustion engine that can vary, for example, the opening / closing timing of an intake valve or an exhaust valve and the valve lift according to the engine operating state.
[0002]
[Prior art]
As this type of conventional valve operating apparatus for an internal combustion engine, one described in SAE 970338 is known.
[0003]
The outline will be described with reference to FIG. 11. The drive shaft 1 is arranged along the front-rear direction on the cylinder head of the engine and is driven to rotate by the crankshaft of the engine, and is swingably supported by the drive shaft 1. For example, the swing cam 4 that slides against the upper surface 3a of the valve lifter 3 of the intake valve 2 to open the intake valve 2 against the spring force of a valve spring (not shown), and the drive shaft 1 swing. A transmission mechanism 5 is provided between the cam 4 and the cam 5 to convert the rotational force of the drive shaft 1 into a lift force and transmit the lift force to the swing cam 4. The transmission mechanism 5 includes a first spur gear 6 fixed to the outer periphery of the drive shaft 1, a crankshaft 7 disposed above the first spur gear 6, and a first spur gear fixed to the crankshaft 7. The second spur gear 8 meshes with the spur gear 6, and a connecting link 10 that links the crankshaft 7 and the swing cam 4 via a connecting pin 9.
[0004]
Then, as the drive shaft 1 and the first spur gear 6 rotate in one direction (arrow), the second spur gear 8 and the crankshaft 7 rotate to cause the connecting cam 10 to swing the swing cam 4 in the arrow direction. Thus, the swing cam 4 is opened and closed by pressing or releasing the pressure against the spring force of the valve spring while the lower cam surface 4a is in sliding contact with the upper surface 3a of the valve lifter 3. It has become. Therefore, a relatively large lift characteristic can be obtained as the valve lift characteristic.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional variable valve operating device, the direction (normal h) of the spring reaction force of the valve spring against the cam surface 4a of the swing cam 4 during one rotation of the drive shaft 1 is the swing cam 4. It is always located inside the connecting pin 9 which is the pivot point of the connecting pin 9, that is, between the connecting pin 9 and the drive shaft 1 as shown in FIG.
[0006]
That is, when the intake cam 2 is opened and closed by pressing or releasing the valve lifter 3 while slidingly contacting the upper surface 3 a of the valve lifter 3, the swing cam 4 is operated via the valve lifter 3. The spring reaction force direction (normal line h) of the valve spring acting on 4 is always located between the shaft center of the connecting pin 9 and the drive shaft 1 regardless of the minimum and maximum lift regions.
[0007]
For this reason, the swing cam 4 is in a state in which the side opposite to the connecting pin 9, that is, the drive shaft 1 side is always pressed upward by the spring force of the valve spring, and therefore, the support hole 4 d that is bearing on the drive shaft 1. The lower end portion 4e of the inner peripheral surface is always in pressure contact with the lower end portion 1b of the outer peripheral surface 1a of the drive shaft 1. As a result, local wear tends to occur between the lower ends 1b and 4e, and the durability may be reduced.
[0008]
[Means for Solving the Problems]
The present invention has been devised in view of the actual situation of the conventional apparatus. The invention according to claim 1 is a drive shaft that rotates in synchronization with a crankshaft of an engine and is provided with a drive cam on the outer periphery. A valve lifter that is slidably supported in the cylinder head and transmits a pressing force to the engine valve, and is swingable through a support hole on an outer peripheral surface of the drive shaft or a support shaft parallel to the drive shaft. As the swinging force is transmitted from a transmission mechanism that transmits the rotational force of the drive cam as a swinging force to a pivot point provided at an end portion of the valve lifter , And a swing cam for opening the engine valve against the spring reaction force of the valve spring by pressing the upper surface thereof, and the pivot point by the spring reaction force of the valve spring. By the moment of rotation Is characterized in that the load direction applied to placing the pivot point in a position such that reversal between the inner peripheral surface and the drive shaft or the outer peripheral surface of the shaft hole.
[0009]
According to the present invention, when the swing cam is in sliding contact with the upper surface of the valve lifter in the large valve lift region of the engine valve, for example, the direction of the spring reaction force of the valve spring is in the base circle region. Although located between the pivot point and the drive shaft, the lift region moves to the opposite side of the drive shaft around the pivot point. Therefore, while it is located between the pivot point and the drive shaft, the sliding contact position of the support hole of the swing cam with respect to the drive shaft is the lower end of the inner peripheral surface of the support hole, but it is located on the opposite side of the drive shaft. In the meantime, since the force acts on the swing cam in the direction in which the drive shaft side is reversed downward with the pivot point as the center, the pressure contact sliding position with respect to the drive shaft is on the upper end side of the inner peripheral surface of the support hole. For this reason, local wear is prevented from occurring between the inner peripheral surface of the support hole of the swing cam and the outer peripheral surface of the drive shaft.
[0010]
The invention according to claim 2 rotates in synchronization with the crankshaft of the engine, and is slidably supported in the cylinder head and provided with a drive cam on the outer periphery, and transmits the pressing force to the engine valve. The valve lifter is supported on the outer peripheral surface of the drive shaft or a support shaft parallel to the drive shaft through a support hole, and the drive cam rotates at a pivot point provided at the end. By transmitting a swinging force from a transmission mechanism that transmits the force as a swinging force, the engine valve is opened against the spring reaction force of the valve spring by pressing the upper surface of the valve lifter as the drive cam rotates. In a state where the swinging cam to be controlled and the valve lift amount of the engine valve are controlled to be small according to the engine operating state, the inner peripheral surface of the support hole and the drive shaft or the support by the spring reaction force of the valve spring Shaft circumference In the state where the load direction is always one side and the valve lift amount is largely controlled by the variable mechanism, the inner periphery of the support hole is caused by the moment around the pivot point by the spring reaction force of the valve spring. The pivot point is arranged at a position where the load direction acting between the surface and the outer peripheral surface of the drive shaft or the support shaft is reversed.
[0011]
Therefore, the valve performance and the valve lift amount can be made variable according to the engine operation state, so that the engine performance can be sufficiently exhibited.
[0012]
In the invention of claim 3, wherein said transmission mechanism includes a link arm having one end slidably fitted into the outer periphery of the drive cam, is provided swingably on the support shaft, one end link A rocker arm that is rotatably linked to the other end of the arm, a link that has one end linked to the other end of the rocker arm, and the other end rotatably connected to the end of the swing cam to constitute the pivot point It is characterized by having a rod.
[0013]
Therefore, since the swing range of the swing cam is always controlled by the transmission mechanism, it is possible to restrict excessive swing over a predetermined amount, for example, at high engine speed.
[0014]
According to a fourth aspect of the present invention, an oil passage is formed in the inner shaft direction of the drive shaft, and an oil hole is formed in the peripheral wall of the drive shaft so as to communicate the oil passage and the inner peripheral surface of the support hole of the swing cam. It is characterized by that.
[0015]
Accordingly, the lubricity between the inner peripheral surface of the support hole of the swing cam and the outer peripheral surface of the drive shaft is improved, and the occurrence of wear between them can be further prevented.
[0016]
According to a fifth aspect of the present invention, the upper surface of the valve lifter that is in sliding contact with the swing cam is formed in an arc shape.
[0017]
According to this invention, the contact position of the cam surface of the swing cam with respect to the valve lifter can be changed, and therefore the direction of the spring reaction force of the valve spring can be easily set from the pivot point to the opposite side of the drive shaft. Can do.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the valve gear of the present invention will be described in detail with reference to the drawings. The valve gear according to this embodiment is provided with a variable mechanism that includes two intake valves per cylinder and that makes the valve lift of the intake valves variable according to the engine operating state.
[0019]
That is, this valve operating device is rotatably supported by a pair of intake valves 12 and 12 slidably provided on a cylinder head 11 via a valve guide (not shown) and a bearing 14 above the cylinder head 11. A hollow drive shaft 13, two drive cams 15 and 15, which are eccentric rotary cams fixed to the drive shaft 13 by press-fitting or the like, and an outer peripheral surface 13 a of the drive shaft 13 are swingably supported. Swing cams 17 and 17 for slidingly opening the intake valves 12 and 12 by sliding contact with valve lifters 16 and 16 disposed at upper ends of the respective intake valves 12 and 12, a drive cam 15 and a swing cam 17, 17, a transmission mechanism 18 that transmits the rotational force of the drive cam 15 as the swinging force of the swing cams 17 and 17, and a variable mechanism 19 that makes the operating position of the transmission mechanism 18 variable. ing.
[0020]
The drive shaft 13 is arranged along the longitudinal direction of the engine and is rotated from the crankshaft of the engine via a driven sprocket (not shown) provided at one end, a timing chain wound around the driven sprocket, and the like. The force is transmitted, and the rotation direction is set in the counterclockwise direction in FIG. In addition, an oil passage 13b communicating with an oil main gallery (not shown) is formed in the direction of the internal axis of the drive shaft 13, and one end of the peripheral wall opens to the oil passage 13b and the other end is connected to the outer peripheral surface 13a. An oil hole 13c opened between the rocking cams 17 and 17 and an inner peripheral surface of a support hole 20a, which will be described later, is formed penetrating along the radial direction.
[0021]
The bearing 14 is provided at the upper end portion of the cylinder head 11 and rotates a main bracket 14a that supports the upper portion of the drive shaft 13, and a control shaft 32 that is provided at the upper end portion of the main bracket 14a and is a support shaft described later. The bracket 14b is supported freely, and both the brackets 14a and 14b are fastened together by a pair of bolts 14c and 14c from above.
[0022]
As shown in FIG. 4, both the drive cams 15 are substantially ring-shaped, and are composed of a small-diameter cam main body 15a and a flange portion 15b integrally provided on the outer end surface of the cam main body 15a. A drive shaft insertion hole 15c is formed penetrating in the direction, and the axis X of the cam body 15a is offset from the axis Y of the drive shaft 13 by a predetermined amount in the radial direction. Each drive cam 15 is press-fitted and fixed to both sides of the drive shaft 13 through the drive shaft insertion hole 15c so as not to interfere with the valve lifters 16 and 16, and both the cam main bodies 15a and 15a are fixed. The outer peripheral surfaces 15d and 15d are formed in the same cam profile.
[0023]
The valve lifters 16 and 16 are formed in a cylindrical shape with a lid, are slidably held in the holding holes of the cylinder head 11, and upper surfaces 16 a and 16 a with which the swing cams 17 and 17 are slidably contacted are in the engine width direction. It is formed in an arc shape along.
[0024]
The swing cam 17 has a substantially U-shape as shown in FIGS. 1 to 3, 6, and 7, and the drive shaft 13 is inserted into a substantially annular base end portion 20 so as to be rotatable. A support hole 20a to be supported is formed through, and a pin hole 21a is formed through the cam nose portion 21 at one end. Further, a cam surface 22 is formed on the lower surface of the swing cam 17, and a base circle surface 22a on the base end portion 20 side, a ramp surface 22b extending from the base circle surface 22a to the cam nose portion 21 side in an arc shape, and the lamp A lift surface 22d is formed from the surface 22b to the top surface 22c of the maximum lift on the distal end side of the cam nose portion 21, and the base surface 22a, the ramp surface 22b, the lift surface 22d and the top surface 22c swing. The upper surface 16a of each valve lifter 16 is brought into contact with a predetermined position according to the swing position of the cam 17.
[0025]
That is, when viewed from the valve lift characteristics shown in FIG. 5, as shown in FIG. 1, the predetermined angle range θ1 of the base circle surface 22a becomes the base circle section, and the predetermined angle range θ2 from the base circle section θ1 of the ramp surface 22b changes. A so-called ramp section is set, and a predetermined angle range θ3 from the ramp section θ2 of the ramp surface 22b to the top surface 22c is set to be a lift section.
[0026]
The transmission mechanism 18 includes a rocker arm 23 disposed above the drive shaft 13, a link arm 24 linking the one end 23 a of the rocker arm 23 and the drive cam 15, the other end 23 b of the rocker arm 23, and a swing cam. 17 is provided.
[0027]
As shown in FIG. 3, each of the rocker arms 23 is bent in a substantially crank shape as viewed from above, and a cylindrical base portion 23c at the center is rotatably supported by a control cam 33 described later. Further, the one end portion 23a protruding from each outer end portion of each cylindrical base portion 23c is formed with a pin hole 23d through which the pin 26 is fitted, while each inner end portion of each base portion 23c is formed through the pin portion 23d. A pin hole 23e into which a pin 27 connected to one end portion 25a of each link rod 25 is fitted is formed in the projecting other end portion 23b.
[0028]
The link arm 24 includes an annular base 24a having a relatively large diameter and a projecting end 24b projecting at a predetermined position on the outer peripheral surface of the base 24a. A fitting hole 24c is formed in the outer peripheral surface of the cam main body 15a of the cam 15 so as to be rotatably fitted. On the protruding end 24b, a pin hole 24d through which the pin 26 is rotatably inserted is formed. Yes.
[0029]
Further, as shown in FIG. 1, the link rod 25 is formed in a straight line having a predetermined length, and the other ends 23b of the rocker arm 23 and the cam nose of the swing cam 17 are provided at both circular ends 25a and 25b. Pin insertion holes 25c and 25d through which the ends of the pins 27 and 28 press-fitted into the pin holes 23e and 21a of the end 21 are rotatably inserted are formed so that the axis 28a of the pin 28 swings. It is the pivot point of the cam 17.
[0030]
The upper surfaces 16a and 16a of the valve lifters 16 and 16 are formed in an arc shape, thereby acting on the moving contact points of the swing cams 17 and 17 and the valve lifters 16 and 16 during the rotation of the drive cams 15 and 15. As shown in FIGS. 7A and 7B, the normal h position, which is the spring reaction force direction of the valve spring, is closer to the drive shaft 13 side around the shaft center 28 a of the pin 28 in the maximum lift region of the intake valve 12. And change to the opposite side. That is, in the base circle region of the swing cams 17, 17, the normal h ₁ that is the direction of the spring reaction force F ₁ of the valve spring is shown in the drawing along the axial direction of the valve stem of the intake valve 12 as shown in FIG. becomes vertical, but has become the drive shaft 13 side toward the axial center 28a, lift in the area, the normal h ₂ is the direction of the spring reaction force F ₂ as shown in FIG. 7B oscillating cams 17, 17 Is set to a position on the opposite side of the drive shaft 13 with the shaft center 28a interposed therebetween so as to contact the outer peripheral edges of the valve lifters 16,16.
[0031]
On the other hand, in the small operating angle region of the intake valves 12 and 12, the swing cams 17 and 17 are always in contact with the substantially central positions of the upper surfaces 16a and 16a of the valve lifters 16 and 16 as shown in FIGS. The lines h ₁ and h ₂ are set so as to be positioned closer to the drive shaft 13 than the axis 28a.
[0032]
In addition, snap rings 29, 30, 31 for restricting the axial movement of the link arm 24 and the link rod 25 are provided at one end of each pin 26, 27, 28.
[0033]
The variable mechanism 19 includes a control shaft 32 that is rotatably supported by the same bearing 14 above the drive shaft 13, and a control cam 33 that is fixed to the outer periphery of the control shaft 32 and serves as a swing fulcrum of the rocker arm 23. It has.
[0034]
Each of the control cams 33 has a cylindrical shape, and the position of the axis P1 is deviated from the axis P2 of the control shaft 32 by α as shown in FIG.
[0035]
The control shaft 32 extends in parallel with the drive shaft 13 and is controlled to rotate within a predetermined rotation angle range by an electromagnetic actuator (not shown) provided at one end, and the electromagnetic actuator is an engine It is driven by a control signal from a controller (not shown) that detects the operating state of the motor. The controller detects the current engine operating state based on detection signals from various sensors such as a crank angle sensor, an air flow meter, and a water temperature sensor, and outputs a control signal to the electromagnetic actuator.
[0036]
The operation of this embodiment will be described below. First, at the time of engine low speed and low load, the electromagnetic actuator is rotationally driven in one direction by a control signal from the controller. For this reason, the control cam 33 is held at the rotational position at the upper left of the axis P2 of the control shaft 32 as shown in FIGS. 6A and 6B, and the thick portion 33a is directed upward from the drive shaft 13. Move away. For this reason, the entire rocker arm 23 moves upward with respect to the drive shaft 13. For this reason, the end portions 23 of each rocking cam 17 are forcibly pulled up slightly via the link rod 25. Rotate left.
[0037]
6A and 6B, when the drive cam 15 rotates and pushes up the one end 23a of the rocker arm 23 via the link arm 24, the lift amount of the rocker cam 17 and the valve lifter is increased via the link rod 25. The lift amount L1 is relatively small as shown in FIG. 6B.
[0038]
Therefore, in such a low-speed and low-load region, as shown by the broken line in FIG. 8, the valve lift amount is reduced, the opening timing of each intake valve 12 is delayed, and the valve overlap with the exhaust valve is reduced. For this reason, improvement in fuel consumption and stable rotation of the engine can be obtained.
[0039]
In this small valve lift region, the normal lines h ₁ and h ₂ of the spring reaction forces F ₁ and F ₂ of the valve spring are closer to the drive shaft 13 than the shaft center 28a. , 17 force f ₁ , f ₂ acting on the outer peripheral surface 13a of the drive shaft 13 from the inner peripheral surface of the support holes 20a, 20a is applied to one band of the lower end portion 20b of the inner peripheral surface and the lower end portion 13d of the outer peripheral surface 13a. However, since the swing valve lift amount of the swing cams 17 and 17 at this time is small, the spring reaction force itself from the valve spring is small and the occurrence of wear between the lower end portions 13d and 20b is small. In addition, at this time, the normal lines h ₁ and h ₂ move only within the region on the swing center side of the swing cam 17, so that a smaller valve lift can be realized.
[0040]
On the other hand, when the engine is shifted at high speed and high load, the electromagnetic actuator is rotationally driven in the opposite direction by a control signal from the controller. Therefore, as shown in FIGS. 7A and 7B, the control shaft 32 rotates the control cam 33 counterclockwise from the position shown in FIG. 6 to move the shaft center P1 (thick portion 33a) downward. For this reason, the entire rocker arm 23 is moved in the direction of the drive shaft 13 (downward), and the other end portion 23b presses the cam nose portion 21 of the swing cam 17 downward via the link rod 25. The entire moving cam 17 is rotated clockwise by a predetermined amount.
[0041]
Therefore, the contact position of the cam surface 22 with respect to the upper surface 16a of the valve lifter 16 of the swing cam 17 moves to the right position as shown in FIGS. For this reason, when the drive cam 15 rotates as shown in FIG. 7A and the one end 23a of the rocker arm 23 is pushed up via the link arm 24, the lift amount L2 with respect to the valve lifter 16 increases as shown in FIG. 7B.
[0042]
Therefore, in such a high speed and high load region, the cam lift characteristic becomes larger than that in the low speed and low load region, the valve lift amount increases as shown by the solid line in FIG. 8, and the opening timing of each intake valve 12 becomes earlier. The closing time is delayed. As a result, the intake charging efficiency is improved and a sufficient output can be secured.
[0043]
Further, the large area of the spring reaction force from the large valve lift area, that the valve spring according to as described above, the contact position of the cam surface 22 relative to the valve lifter 16 top 16a is as shown in FIG. 7B, the upper surface in the vicinity of the maximum lift to become near the hole edge of 16a, the normal h ₂ of the spring of the valve spring reaction force F ₂ is outside the axis 28a, that is, on the opposite side of the drive shaft 13 by sandwiching the axial center 28a. Accordingly, the swing cams 17 and 17 are acted on by a counterclockwise moment M in the drawing with the shaft center 28a as a fulcrum as a whole, and this time, they are pressed downward by the load f ₂ and thereby the inner periphery of the support hole 20a. The load direction is reversed so that the upper end portion 20c of the surface slides against the upper end portion of the outer peripheral surface 13a of the drive shaft 13.
[0044]
As a result, the supporting pressure slide between the lower end portion 20b of the hole 20a in the peripheral surface and the lower end portion 13d of the outer peripheral surface 13a of the drive shaft 13 is avoided, the both lower ends 13 d, and 20b local heat generation and wear of the Occurrence is prevented.
[0045]
Moreover, since lubricating oil is supplied from the oil passage 13b and the oil hole 13c between the inner peripheral surface of the support hole 20a and the outer peripheral surface 13a of the drive shaft 13, the lubrication performance between both surfaces is improved. In addition, as described above, the so-called squeezing film effect of the lubricating oil occurs when the load is reversed, and the load capacity of the lubricating oil is improved, and the lubricating oil is forcibly supplied to the contact portion between both surfaces when the load is reversed Therefore, it is possible to further prevent the occurrence of wear between both surfaces.
[0046]
Further, since the swinging range of the swing cams 17 and 17 is controlled by the transmission mechanism 18, particularly the link rod 25, even if the swing speed increases at a high engine speed or the like, the swing cams 17 and 17 are excessively swung over a predetermined amount. Movement can be regulated.
[0047]
FIG. 9 shows a second embodiment of the present invention, in which the link rod 25 is bent into an arc shape having a concave shape on the drive shaft 13 side, and the upper surfaces 16a, 16a of the valve lifters 16, 16 are formed flat. . Accordingly, link by bending forming a rod 25 in an arc, a normal h ₂ of the blade reaction force of the valve spring to lift area in the maximum lift region of the first embodiment similarly to the intake valve 12 is the axis 28a It is comprised so that it may be located outside. Other configurations are the same as those of the first embodiment.
[0048]
Therefore, this embodiment also prevents local wear between the outer peripheral surface 13a of the drive shaft 13 and the inner peripheral surface of the support hole 20a of the swing cams 17 and 17.
[0049]
FIG. 10 shows a third embodiment of the present invention, in which the swing cam 22 is supported on a support shaft 100 independent of the drive shaft 13. An oil passage 101 is formed in the direction of the internal axis of the support shaft 100, and an oil hole 102 having one end opened to the support hole 200 of the swing cam 17 is formed in the peripheral wall. In this embodiment, since the force f ₂ from the swing cam 22 does not act on the drive shaft 13, local wear of the drive shaft 13 can be prevented and durability is improved. On the other hand, the wear resistance of the support shaft 100 is improved by the same principle as described above (the embodiment). Other configurations are the same as those of the first embodiment.
[0050]
In addition, this invention is not limited to the structure of the said embodiment, For example, this apparatus can also be applied to the exhaust valve side, and can also be applied to the apparatus which does not have the variable mechanism 19. FIG.
[0051]
【The invention's effect】
As is apparent from the above description, according to the valve operating device of the present invention, the inner peripheral surface of the support hole and the drive shaft or the support shaft are caused by the moment around the pivot point due to the spring reaction force of the valve spring. Since the pivot point is arranged at a position where the load direction acting between the outer peripheral surface and the outer peripheral surface is reversed , local wear between the inner peripheral surface of the swing cam support hole and the outer peripheral surface of the drive shaft or the support shaft is prevented. Occurrence can be prevented.
[0052]
According to the second aspect of the present invention, the valve timing and the valve lift amount of the engine valve can be made variable by the variable mechanism, so that the engine performance corresponding to the engine operating state can be sufficiently exhibited.
[0053]
According to the third aspect of the present invention, excessive swinging of the swing cam at, for example, high engine speed is restricted by the mechanical transmission mechanism, and therefore the valve timing and valve lift can be controlled with high accuracy.
[0054]
According to the fourth aspect of the present invention, the lubrication performance between the inner peripheral surface of the support hole of the swing cam and the outer peripheral surface of the drive shaft can be greatly improved, and the occurrence of wear between both surfaces can be further prevented. become.
[0055]
According to the fifth aspect of the present invention, since the contact position of the cam surface of the swing cam with respect to the valve lifter can be changed, the direction of the spring reaction force of the valve spring is changed from the pivot point to the outer side opposite to the drive shaft. Can be set easily. In addition, by forming the upper surface of the valve lifter in an arc shape, it is possible to increase the reversal moment of the valve spring spring reaction force with respect to the aforementioned swing cam, so that the inner peripheral surface of the support hole and the outer peripheral surface of the drive shaft The effect of reducing wear can be further improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view taken along line AA of FIG. 2 showing a first embodiment of the present invention.
FIG. 2 is a side view showing a part of the embodiment.
FIG. 3 is a plan view of the embodiment.
FIG. 4 is a perspective view showing a drive cam used in the embodiment.
FIG. 5 is a valve lift characteristic diagram corresponding to a base end surface and a cam surface of a swing cam.
FIGS. 6A and 6B are cross-sectional views taken along line BB in FIG.
FIGS. 7A and 7B are cross-sectional views taken along line B-B in FIG.
FIG. 8 is a characteristic diagram of valve timing and valve lift according to the present embodiment.
FIG. 9 is a cross-sectional view showing a second embodiment of the present invention.
FIG. 10 is a cross-sectional view showing a third embodiment of the present invention.
FIG. 11 is a schematic view showing a conventional valve gear.
FIG. 12 is an operation explanatory view of the conventional valve gear.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Cylinder head 12 ... Intake valve 13 ... Drive shaft 13a ... Outer peripheral surface 13d ... Lower end part 13e ... Upper end part 15 ... Drive cam 16 ... Valve lifter (follower)
17 ... oscillating cam 18 ... transmission mechanism 19 ... variable mechanism 20 ... base 20a ... support hole 20b ... lower end 20c ... upper end 21 ... one end 22 ... cam surface 23 ... rocker arms 23a, 23b ... end 24 ... link arm 25 ... Link rod 28 ... Pin 28a ... Axis center (Pivot point)

Claims

A drive shaft that rotates in synchronization with the crankshaft of the engine and is provided with a drive cam on the outer periphery;
A valve lifter that is slidably supported in the cylinder head and transmits a pressing force to the engine valve;
The drive shaft or a support shaft parallel to the drive shaft is swingably supported through a support hole, and the rotational force of the drive cam is used as a swing force at a pivot point provided at the end. A swing cam that opens the engine valve against the spring reaction force of the valve spring by pressing the upper surface of the valve lifter as the drive cam rotates by transmitting the swing force from the transmission mechanism A valve operating apparatus for an internal combustion engine comprising:
The pivot is moved to a position where the load direction acting between the inner peripheral surface of the support hole and the outer peripheral surface of the drive shaft or the support shaft is reversed by the moment about the pivot point due to the spring reaction force of the valve spring. A valve operating apparatus for an internal combustion engine, wherein a fulcrum is arranged.

A drive shaft that rotates in synchronization with the crankshaft of the engine and is provided with a drive cam on the outer periphery;
A valve lifter that is slidably supported in the cylinder head and transmits a pressing force to the engine valve;
The drive shaft or a support shaft parallel to the drive shaft is swingably supported through a support hole, and the rotational force of the drive cam is used as a swing force at a pivot point provided at the end. A swing cam that opens the engine valve against the spring reaction force of the valve spring by pressing the upper surface of the valve lifter as the drive cam rotates by transmitting the swing force from the transmission mechanism ,
A variable mechanism for variably controlling the valve lift amount of the engine valve according to the engine operation state,
In a state where the valve lift is controlled to be small by the variable mechanism, the load direction between the inner peripheral surface of the support hole and the outer peripheral surface of the drive shaft or the support shaft due to the spring reaction force of the valve spring is always In the state where the valve lift amount is largely controlled by the variable mechanism on one side, the inner peripheral surface of the support hole and the drive shaft or the support shaft are caused by the moment around the pivot point due to the spring reaction force of the valve spring. A valve operating apparatus for an internal combustion engine, characterized in that the pivot point is disposed at a position where a load direction acting between the outer peripheral surface and the outer peripheral surface of the internal combustion engine is reversed.

The transmission mechanism includes a link arm having one end slidably fitted to the outer periphery of the drive cam, and a swing shaft provided on the support shaft. The one end is rotatably linked to the other end of the link arm. A rocker arm, and a link rod that has one end linked to the other end of the rocker arm and the other end rotatably connected to the end of the swing cam to constitute the pivot point. The valve gear for an internal combustion engine according to claim 1 or 2.

An oil passage is formed in an inner axial direction of the drive shaft, and an oil hole is formed in a peripheral wall of the drive shaft to communicate the oil passage and an inner peripheral surface of a support hole of a swing cam. 3. A valve operating apparatus for an internal combustion engine according to 1 or 2.

3. The valve operating apparatus for an internal combustion engine according to claim 1, wherein an upper surface that is in sliding contact with the swing cam of the valve lifter is formed in an arc shape.